The white "cloth" you see is actually athletic tape. My son, who has Osgood-Schlatter's, puts two layers of tape under his patella during the summer and wears knee braces during the winter. He tried kinesio tape as well, and he really enjoyed it until it irritated his skin. It's not what you see on their knees, though.

It's a "patella strap." Links below for your reference. Do a little research before blindly strapping some gadget onto your knee. If you have no previous problems, don't try to fix something that ain't broke.

As far as method of doing so, athletic tape works, but a "pro tip" i've seen in the past is actually to use panty hose. Cut the bottom out of the panty hose, and then roll it upwards (on your leg, obviously) until it makes a donut shape. This is much more flexible than Athletic tape (also you don't have to deal with the pulling-out-of-leg-hair problems that you would with AT).

We go to a lot of meets and tournaments for my kids. The trainers will put a few turns of foam pre tape on, then roll it up and place it just below the knee cap. It's cheap, everyone should have it in their bag and you can pick colours to match your racquet:shock: